Electrically insulating tape and method of applying same

ABSTRACT

AN ELECTRICALLY INSULATING TAPE COMPRISING A THIN ROBBON OF FLEXIBLE ELECTRICALLY INSULATING MATERIAL WITH ADHESIVE ON ONE FLAT SURFACE AND IN CONTACT WITH A LOW RELEASE BACKING MATERIAL. OPENINGS SPACED ONE FROM ANOTHER ARE PROVIDED ALONG THE LENGTH OF THE TAPE. UPON REMOVAL OF THE BACKING MATERIAL, THE TAPE IS APPLIED TO AN ELONGATED SURFACE HAVING A DIMENSION LESS THAN THE WIDTH OF THE OPEN-   INGS AND TRIMMED TO LEAVE ON THE ELONGATED SURFACE ONLY THOSE PORTIONS OF THE TAPE INTERMEDIATE THE OPENINGS.

9 1, Y T. A. DE WINTER E 3,$23924 ,ELEQIRI CALLY INSULATING TAPE ANDMETHOD OF APPLYING SAME 4 Sheets-Sheet 1 Filed Dec; 15, 1969 m R m E m wMNW l A WWL MJM ARM O EWl H BY ATTORNEYS 0v. 30, 1971 DE wm'r ETAL3,623,924

ELECTRICALLY INSULATING TAPE AND METHOD OF APPLYING SAME Filed Dec. 15,1969 4 Sheet::-Sheet 8 THEO A. DE WINTER EDWARD J. LUCAS WILLIAM A.LANYI INVENTOR.

BY I wmil ATTQRNEYS Nov. 30, 1971 T. A. DE WINTER ETAL 3,623,924

ELECTRICALLY INSULATING TAPE AND METHOD OF APPLYING SAME Filed Dec. 15,1969 4 Sheets-Sheet 5 THEO A. DE WINTER EDWARD J. LUCAS WILLIAM A. LANYIINVENTOR.

BY Mwy ATTORNEYS NOV. 30, 1971 T, 35; w R ETAL 3,623,924

ELECTRICALLY INSULATING TAPE AND METHOD OF APPLYING SAME Filed Dec. 15,1969 4 Sheets-Sheet &

THEO A. DE WINTER l5 EDWARD J. LUCAS WILLIAM A.LANY| INVENTOR.

ATTOR NEYS United States Patent Oifice 3,623,924 ELECTRICALLY INSULATINGTAPE AND METHOD OF APPLYING SAME Theo A. de Winter, Methuen, Edward J.Lucas, Wayland, and William A. Lanyi, Boxford, Mass., assiguors to AvcoCorporation, Cincinnati, Ohio Filed Dec. 15, 1969, Ser. No. 884,905 Int.Cl. H01b 7/03, 13/06 US. Cl. 156-51 4 Claims ABSTRACT OF THE DISCLOSUREAn electrically insulating tape comprising a thin ribbon of flexibleelectrically insulating material with adhesive on one fiat surface andin contact with a low release backing material. Openings spaced one fromanother are provided along the length of the tape. Upon removal of thebacking material, the tape is applied to an elongated surface having adimension less than the width of the openings and trimmed to leave onthe elongated surface only those portions of the tape intermediate theopenings.

The use of superconducting materials in large electromagnets has pointedup the importance of stabilization. Stabilization is achieved when a lowresistance normal substrate is intimately bonded to the superconductor,and this substrate is maintained below the critical temperature of thesuperconductor, even when carrying the entire current. Several factorsdetermine the operating temperature of the substrate when the currentcarried by the conductor runs exclusively in the normal substrate. Themost important of these factors are the electrical resistivity of thesubstrate, the cross-sectionalarea of the substrate, and the resistanceto heat transfer between the surface of the conductor and the liquidhelium environment. This last factor is directly related to the fractionof surface area exposed to the liquid helium. Any heat transfer throughelectrical insulation will encounter a high thermal resistance. It istherefore desirable in the design of a stabilized superconducting magnetto have part of the conductor surface in direct contact with a suitablecoolant such as liquid helium. This cannot be achieved if the conductoris insulated over its complete outer surface. An intermittent type ofinsulation which provides turn to turn separation and electricalinsulation and yet allows liquid helium to contact part of the insulatedfaces of the conductor will solve this problem.

In the foregoing, it will be clear that one of the primary objects ofthe invention is to provide a method of applying intermittent electricinsulation.

Another object of the invention is to provide a method of applyingintermittent electrical insulation to an electrical conductor at aboutthe time it is to be used.

A further object of the invention is to provide a method of applyingintermittent electrical insulation to an electrical conductor whichpermits simple and quick variation of the type and amount of insulationapplied.

A still further object of the invention is to provide an electricallyinsulating tape for use in providing intermittent electrical insulationon electrical conductors.

The novel features that are considered characteristic of 3,623,924Patented Nov. 30, 1971 the invention are set forth in the appendedclaims; the invention itself, however, both as to its organization andmethod of operation, together with additional objects and advantagesthereof, will best be understood from the following description of aspecific embodiment when read in conjunction With the accompanyingdrawings, .in which:

FIG. 1 is a fragmentary perspective view of an electrically insulatingtape in accordance with the invention;

FIG. 2 is a fragmentary perspective view of a modified electricallyinsulating tape in accordance with the invention;

FIG. 3 is a fragmentary perspective view illustrating how theelectrically insulating tape is trimmed after being applied to aconductor;

FIG. 4 shows diagrammatically the application of electrically insulatingtape to a conductor in accordance with the invention;

FIG. 5 is a fragmentary perspective view of a conductor insulated withthe tape of FIG. 1; and

FIG. 6 is a fragmentary perspective view of a ribbon conductor insulatedwith the tape of FIG. 2.

Directing attention now to FIG. 1, there is shown in greatly enlargedform for purposes of clarity an electrically insulating tape inaccordance with the invention and designated generally by the numeral11. The tape 11 comprises a flexible electrically insulating ribbon 12of suitable material such as Mylar. Provided on one fiat surface of theinsulating ribbon 12 is a suitable adhesive 13 which may be covered by aribbon of suitable low release backing material 14 of the same width asthe insulating ribbon 12. Provided along the length or longitudinaldirection of the tape 11 are a plurality of openings or holes 15 passingentirely through the tape and spaced one from another in thelongitudinal direction of the tape. The openings 15 have a dimension inthe width or transverse direction of the electrically insulating ribbonthat is less than the width of the tape as shown. Each opening isdefined by sides 16 and 17 substantially parallel to the longitudinalaxis of the tape and substantially parallel sides 18 and 19 normal tothe longitudinal axis of the tape.

In FIG. 2 is shown a modified tape 11a wherein openings 21 aresubstantially rectangular in shape but disposed at an angle of about 45to the longitudinal axis of the tape. The openings 21 in the tape may beconveniently provided by passing the tape through a punch adapted topunch out holes of the desired configuration, orientation and spacing.

As shown in FIGS. 3 and 4, insulation is provided on a conductor 22 bypeeling off the low release backing where present and bringing theadhesive into contact with the surface 23 of the conductor to beprovided with insulation and the tape 11 applied to this surface as bypressing, rolling, and the like. The openings and, hence, the tapeitself are Wider than the surface of the conductor to be provided withinsulation. After the adhesive has been pressed on to the surface to beinsulated, the conductor with the tape is passed between two trimmerknives 24 and 25 which cut the tape intermediate the openings, therebyleaving on the conductor most of that portion of the tape intermediatethe openings.

FIG. 5 shows a rectangular superconductive conductor 22 insulated withthe tape 11 of FIG. 1 and FIG. 6 shows a ribbon superconductiveconductor 41 insulated with the tape 11a of FIG. 2.

'In one case as a superconductive coil was being wound, Mylar tape inaccordance with FIG. 1 was applied to a face .086" wide on a rectangularsuperconductive conductor 22 as shown in FIG. 5. The tape comprisedconventional adhesive coated Mylar tape wide and .0065" thick. This tapewas put on a low release backing and using a die wide and by A" long,openings of this size were punched out of the tape and the backing. Theopenings were spaced /2 apart to leave portions 42 of the tape /2 longbetween openings (see FIG. 1). The tape was applied substantially asshown in FIG. 4 and trimmed substantially as shown in FIG. 3. Theresults were substantially as shown in FIG. 5.

In another case Mylar tape in accordance with FIG. 2 was applied to a/2" wide superconductive ribbon conductor 41 as shown in FIG. 6. In thiscase the tape comprised conventional Mylar tape l wide and .0035 thick.This tape was put on a low release backing and die punched to provide A"wide openings oriented 45 to the longitudinal axis of the tape as shownin FIG. 2. The openings spanned three-fourths of the width of the tapeand were spaced apart to leave portions 43 between openings (see FIG.2). Application of this tape in accordance with the invention providedthe result as shown in FIG. 6.

Where the insulating material is punched prior to application of theadhesive, the backing material may be omitted if the adhesive permitswinding of the tape into rolls in conventional manner.

It will now be apparent that the present invention permits theapplication of intermittent insulation of any desired coverage eitherprior to or preferably while the conductor is being wound into a coil ordevice.

The various features and advantages of the invention are thought to beclear from the foregoing description. Various other features andadvantages not specifically enumerated will undoubtedly occur to thoseversed in the art, as likewise will many variations and modifications ofthe preferred embodiment illustrated, all of which may be achievedwithout departing from the spirit and scope of the invention as definedby the following claims.

We claim:

1. The method of applying intermittent insulation to an electricalconductor comprising:

(a) bringing a flexible electrically insulating tape into contact withsaid electrical conductor, said tape hav- 4 ing an adhesive surfacedisposed for contact with said conductor, said tape being wider thansaid conductor and provided with a plurality of openings spaced one fromanother and having a dimension greater than the width of said conductor;

(b) pressing said adhesive surface into contact with said conductor; and

(c) passing said conductor with said tape attached thereto past trimmerknives adapted to engage and cut said tape intermediate said openingsand adjacent each longitudinal edge of said tape.

2. The method as defined in claim 1 wherein said conductor has anelongated fiat surface defining one side thereof, and only the middleportion of said tape intermediate said openings is pressed into contactwith said conductor.

3. The method as defined in claim 2 wherein said openings have adimension normal to the longitudinal axis of said tape that is greaterthan the width of said flat surface.

4. The method as defined in claim 3 wherein two trimmer knives are eachdisposed adjacent a different longitudinal edge of said flat surfacewhereby as said tape and conductor are passed between said trimmerknives said tape is cut only intermediate said openings andsubstantially parallel to the longitudinal axis of said tape adjacentthe edges of said tape whereby only portions of said tape intermediatesaid openings remain adhered to said surface spaced apart a distancesubstantially equal to the longitudinal spacing of said openings in saidtape.

References Cited UNITED STATES PATENTS 3,514,730 5/1970 Kassner 335-216BENJAMIN A. BOROHELT, Primary Examiner H. TUDOR, Assistant Examiner

